Pumping device for deep oil wells



Jan. 23, 1968 P. GHEORGHE 3,364,864

PUMPING DEVICE FOR DEEP OIL WELLS Filed March 17, 1965 5 Sheets-Sheet 19 J J 9 A- -A Inventor:

Gheor he PETRESCU by: m? 0 I661";

Jan; 23, 1968 P. GHEORGHE 3,364,864

PUMPING DEVICE FOR DEEP OIL WELLS Filed March 17, 1965 s Sheets-Sheet 2Fig. 3

lnVenzor: V GheorhePETRESCU his Affor'ney Jan. 23, 1968 P. GHEORGHE3,364,864

PUMPING DEVICE FOR DEEI OIL WELLS Filed March 17, 1965 5 Sheets-Sheet 5lnvenzor: Gheorghe PETRESCU b y.- vii/lam 0. 5%

his Afforney Jan. 23, 1968 P. GHEORGHE 3,364,864

PUMPING DEVICE FOR DEEP OIL WELLS Filed March 17, 1965 5 Sheets-Sheet 4lnvenzor: Gheorghe PETRESCU A um (Q 6% his Affqrney Jan. 23, 1968 P.GHEORGHE 3,3 w

PUMPING DEVICE FOR DEEP OIL WELLS Filed March 17, 1965 5 Sheets-Sheet 5mg. a

Inventor: Gheorghe PETRESCU by:

his Afl'onney United States Patent Ofifice 3,364,864 Patented Jan. 23,1968 3 364 864 PUMPHNG DEVICE; FilR DEEP OIL WELLS Petrescu Gheorghe,Str. Lisahona 3, Bucharest, Rumania Filed Mar. 17, 1965, Ser. No.440,455 Claims priority, application Rumania, Mar. 21, 1964, 47 695Claims. Eel. 103-46) This invention relates to an installation for oilpumping, the working conditions of which are not influenced by thepumping depth.

The pumping method using piston pumps driven from the surface bysucker-rods-string actuated with a reciprocating motion by a walkingbeam connected to a pitman and by a speed reducing gear, coupled with anelectric motor is known in the art.

system can be used is limited by the sucker-rods-string ultimate tensilestrength, under the strain of the dead weight of the string and theactuating forces of the pump.

It is also known to use a pumping method which employs a centrifugalpump directly couples with a threephased asynchronous motors. Thedisadvantage of this known pumping method consists in the fact that, athigh pressures of over 200 kg./sq. cm, under which the pump has to workat these depths, the dimensional limitations for the construction of thecentrifugal pump within the space restriction of the well casing demandsa large number of stages (250-300 stages), a fact which complicates verymuch the construction, raises the capital investment, increases thedanger of the impellers being eroded by the sand contained in the oil,and reduces greatly the operating efficiency.

There are also known in the art pumping devices using electromagneticdrives by using solenoid type coils which, due to a shifting magneticfield produced by the threephased currents, produce alternating magneticforces on the magnetic armature solid secured to the piston of the pump.

Also forming part of the prior art is, for example, the device disclosedin US. Patent No. 1,740,003 entitled, Electrically Driven Oil Well Pump.This device uses a double piston pump driven by a cylindrically shapedthreephased induction motor, which imparts a rectilinear reciprocalmotion to a double piston. This double piston can advantageously bepositioned inside well holes, since the double piston is axially mountedinside the mobile armature. The stator of the motor for the device iscomposed of annular sections between which annular spaces are providedfor the coils of the stator, which alternately are connected to one ofthe three phases of an electric power source. The interrupting of thecurrent and the reversal of the phases at the end of the strokes inorder to reverse the direction of motion of the double piston iseffectuated by well known switching means. This type of a device has theinherent weakness of requiring the reversing of the direction of motionof the double piston at relatively high frequencies to 60 strokes perminute) which leads to two unfavorable effects:

A rapid wear of the contactors used for reversing the current;

An excessive coil heating, due to the very big starting currents whichappear at each direction change.

The pumping device disclosed in US. Patent No. 1,740,- 003 has thefurther disadvantage that the pump, which is mounted within the mobilearmature of the electric motor, requires, of course, an increase in theoutside diameter of the motor itself, which reduces the possibilities ofusing this device for pumping oil in deep wells, where only smalldiameter casings are used. Since the stator of the motor consists ofannular sections, there is furthermore an inherent disadvantage in theconstruction of the electric motor itself because the magnetic forcelines of the magnetic multipolar field act transversely to these annularsections by passing through the spaces between the magnetic sheets,which means an increase of the air gap, which in turn has a negativeeffect on the maximum power output of the device, the power requirementfor the starting forces, etc.

The above mentioned disadvantages of the known oil pumping systems fordeep wells are eliminated by the pumping installation according to thisinvention, due to the fact that it is using two pumps directly actuatedby an induction electric motor with rect'ilineal alternating motionhaving a construction fitted to the overall dimensions of the Wellcasing and due to the fact that the device of this invention eliminatesthe unfavorable effects caused by the high frequency reversal of motionpresent in the prior art devices by the following means taken separatelyor combined:

In the device of this invention the requirement for producing largeforces during each direction reversal of the pump by electrical meanshas been eliminated. In lieu thereof, there is used a hydraulic devicefor starting and reaching the normal speed. This hydraulic drive iseffectuated by the pressure caused by the pumped liquid, which isapplied to one piston of the device, while simultaneously beingeliminated at the other, in accordance with the direction of the movingarmature of the device. In this manner, in the device of this inventionduring the starting period one of the pumps is being energized by ahydraulic force, while the other is idling. Consequently, despite thefact that the device has an alternating rectilinear motion, the electricmotor is operating, insofar as its power input is concerned, with apractically constant speed and with rigorously maintained constanttraction forces.

Furthermore, the mechanical current breaking arrangements of the priorart devices for interrupting the current supply at each direction changeof the pump have been eliminated. In lieu thereof, there are usedstationary electronic means which are controlled by the motion of themobile armature.

Several illustrative embodiments of pumping devices in accordance withthis invention, together with additional objects and advantages thereof,will be best understood from the following description of specificembodiments when read in connection with the accompanying drawing inwhich:

FIG. 1 is a cross-sectional elevation illustrating a general set up ofthe pumping device of this invention;

FIG. 2 is a transverse cross-section through one embodiment of anelectric motor of the device of this invention;

FIG. 3 is a longitudinal cross-section through the electric motorillustrated in FIG. 2;

'FIG. 4 is a cross-sectional view of another embodiment of an electricmotor in accordance with this invention;

FIGS. 5a and 5b are cross-sectional elevations illustratingschematically the electric and hydraulic drives of the device of thisinvention;

FIG. 6 is an electric circuit diagram for the motion direction changingmeans of the device.

Referring specifically to the drawing there is illustrated in FIG. 1,the electric motor M which drives two piston pumps P and P which havealternating active strokes, one having an ascending stroke while theother has a descending stroke. With this arrangement both of the strokesof the electric motor M are active, which fact reduces to a halt" thepower loses in the motor winding when comparing the device of thisinvention with these prior art devices employing a single pump which forthe same output has one active stroke and one idle stroke.

In order to ensure a good insulation of the coils, taking intoconsideration the fact that the motor is immersed in oil, the housingshell of the motor M is made fluidtight and is filled with :air or withinsulating oil, which is serving as cooling fluid as well.

One constructional arrangement of the electric motor M is illustrated inFIG. 4. The electric motor is of the poly-'phase indu'ction type havingits secondary mounted in a squirrel cage. A cylindrical housing 1 inwhich there are mounted several stators S S each of which is composed ofa plurality of radially disposed sheets. Each stator S is provided withradially extending teeth and slots. The coils for an armature A aremounted within the slots. The armature A is axially mounted in the motorM and is, due to the action of the shifting magnetic field produced inthe air gaps, alternatively moving in the vertical direction.

In order to obtain the stroke lengths and pumping frequencies comparableto those obtained with ordinary oil well pumps (20 30 double strokes of2 4m.

.per minute) while using currents of industrial frequency,

the electric motor M is provided with a great number of pole pairs,having a poler pitch as short as possible, and having thus the smallestpossible number of slots per pole and phase, preferably only one slot.The oil terminals 3 of the statoric winding are obtained by passing thewinding from a stator S slot to a stator S slot, inasmuch to allow themagnetic flux lines of force to pass farther from a stator to another,alternating the direction from a pole to another.

The mobile armature A is provided with two ladder shaped plane cages,constituted each from active bars 4 placed inside the slots and with hteends welded to two rectilineal strips 5, which act as the rotor ringsfor the squirrel cage type motor.

The mobile armature A extends beyond the stator a distance equal to thestroke length, and is alternatively moving on two slide bars 6 securedto the two stators, causing, by means of rods 7, the movement of thepistons 8. The motor winding is cooled by displacing in an inversedirection the fluid from inside the housing. The oil pumped by the lowerpump is delivered upwardly through the pipe lines 9.

The motor housing is provided with two stufiing-boxes 10. For thebalancing of the pressure from the housing with the external pressureadequate balancing devices are used.

The connection between the two pumps and the tubing string 11, is madeby means of a pipe line 12 and the suction of the upper pump is eifectedvia the pipe 13.

The stufling boxes 10, are provided in order to absorb shocks when thepump exceeds its normal stroke.

In order to utilize to the 'fullest extent the small interior diameterof the casing a great number of stators may be used.

In the embodiment illustrated in the transverse crosssectional view ofFIG. 4, six stators S -S each having the shape of a circular arc, aremounted directly in the housing. In this arrangement, the coil terminals15 are almost completely eliminated, the coils passing directly from theslot of one stator to the slot of an adjacent stator, thus passingthrough all six stators.

The coil of one slot is connnected in series with the coil of the otherslots shifted so that a predetermined number of slots correspond to apair of poles. Consequently, the winding is composed of coilscorresponding to the number of phases and to the number ofpoles, ofwhich half are connected inversely to the other half, in order to obtainalternatively the north and south polarities.

The manufacturing of the winding can be simplified by choosingcompletely open slots and pressing successively from the exterior, andin .a radial direction, the six stators upon the winding previouslyprepared on a cylindrical mandrel with a corresponding diameter.

The mobile armature A has a length equal to that of the stators plus thelength of the stroke. It is displaced alternatively, being guided by therollers r r secured to both ends of the stators. It efi'ectuates thereciprocal motions of the pistons via the rod 7 and also etlectuates thedisplacement on the inverse sides of the cooling liquid present in theradial spaces U U near the coil terminals 15.

The mobile armature A for the embodiment of FIG. 4 has a cylindricalshape being made out of sheets or solid steel and is provided with teethand slots which contain the Winding consisting of a single annularconductor for each slot. Thus, the armature A forms a cylindrical cagehaving annular bars. 7

In the center of the mobile armature A there is provided a channel 11,which ensures the cooling of the mobile armature A by means of thecirculating liquid.

The housing shell 1 of the motor illustrated in FIG. 4 has a lengthequal to that of one of the stators 8 -8 plus double the length of thestroke so as to be able to accommodate the stroke of the mobile armatureA.

The housing shell 1 of the motor is sealed at its top and bottom by thestufiing boxes 10 from the liquid under pressure in the well hole. Thehousing shell 1 includes means for permitting an expansion of thecooling liquid. In order to absorb shocks that may occur under highfrequency operation of the armature A, damping springs 14 are coaxiallymounted on the upper and lower rods 7.

Both pumps P and P are connected via ducts 9 to the tubing 11, suctionby pumps taking place through the intake ducts.

In the embodiments of FIGS. 5a and 5b there are illustrated theelectrohydraulic driving systems which allow starting at the end of thestrokes when the motion direction is reversed, by using the hydraulicpressure exerted by the pumped oil column and acting upon the pumppistons.

In FIG. 5a there is illustrated an embodiment in which both the pumps Pand P are assembled in a single cylinder 17, mounted above the electricmotor M and being provided at their respective stroke ends with twodischarge valves 18 and 18' and two suction valves 19 and 19, and towardthe middle of the common piston housing, with two valveless windows 20and 20, which are shut and opened directly by the motion of therespective pistons.

Inside the cylinder 17 and on the common rod 21 driven by the electricmotor are mounted two pistons 22 and 22' provided each with a slideplate 23 and'23' which serves to keep open the respective dischargevalves 18, during the starting period by hydraulic action, thusfunctioning like a car with rectilineal motion.

The electric pump acted on by the hydraulic drive operates as follows:

During the down stroke, due to the. action of the electric motor M, thepiston 22, pressing the oil in the cylinder, keeps the suction valve 19shut (which during suction is opened toward the interior pressing uponits spring) and causes the discharge valve 18 to open (which openstoward the outside, and which during the suction is kept closed by itsspring), discharging through it the oil from cylinder.

'When approaching the end of the stroke, the electric current is cut-01fby the switching-reversing device illustrated in FIG. 6 and the pistonmotion is checked by the pressure exerted by the discharged oil column.

At the end of the down stroke the oil discharge action ceases and thevalve 18 closes under the pressure of its spring and due to pressure ofthe delivered oil column, but is kept open by the slide-bar 23, so thatthe oil column can further exert its pressure upon the piston.

During its down stroke (which is really an up stroke), the other piston22 is working under suction, with the suction valve 19 open under thepressure of the oil from the oil well, which enters into the free spaceleft in the cylinder caused by the piston displacement, during which thecorresponding discharge valve 18 is closed.

When the piston 22' approaches the lower end of the stroke, it passesslightly beyond the window 20', thereby establishing communication withthe outside, so that only the pressure, of the liquid in the oil well isexerted upon this piston, while upon the piston 22 there is exerted thelarger pressure of the discharged oil column, causing the entire mobilestring to start an inverse motion, by hydraulic action. At the pointwhere the mobile string has reached its normal speed, the slide-bar 23(correspondingly adjusted) ceases to maintain open the lower dischargevalve 18, the piston 22 during its upstroke closes the window 20, andthe device for switching and reversing reestabilshes the electriccurrent in the circuit, in the corresponding direction, so that theelectric pump passes from an hydraulic drive to an electric drive.

The upstroke being continued due to the action of the electric motor M,the piston 22' discharges the oil from the cylinder through the valve18' and the piston 22 is practicing suction witht he discharge valve 18closed and the suction valve 19 opened by the pressure of the oil fromthe oil well, which enters in the void left behind the piston.

At the end of the upstroke, the braking of the mobile string and itsstart in a reverse direction is elfectuated in conditions similar to thedownstroke, due to the action of the discarge valve 18 controlled by theslide-bar 23', and due to the opening of window 20 by the piston 22.

In this manner, by combining the hydraulic drive at the beginning of thestroke, with the electric drive during the rest of the stroke, aconstant speed and a constant driving force by the electric motor isobtained, and thereby the unfavorable effects of direction reversals ofthe structure that appear during the running of asynchronous electricmotors with alternative rectilineal motion are completely eliminated,the hydraulic action can be complemented advantageously by havingcompression springs act during the braking period, which by theirsubsequent expansion which takes place in the period of starting thevertically moving parts in a reverse direction, aid in the directionreversals. These springs may be advantageously mounted at the strokeends.

In the constructional arrangements illustrated in FIG. 5b, the cylindersof the pump are separated from the electric motor housing by using twoseparate stuffing boxes, one (24) adjacent to the electric motor and theother (25) adjacent to the pump. The two pumping compartments and theappurtenant valves are arranged adjacent to each other at the middle ofthe cylinder of the pumps, being separated by a common wall, throughwhich the actuating rod of the upper piston is passing and which needsonly a single stufiing box, the sealing means of which are underpressure, and the direction of which continuously alternates whichreduces the possibility of leakage of liquid under pressuretherethrough.

In the embodiment of the pump illustrated in FIG. 5a, where the twopumps P and P are mounted above the electric motor M, the pumpingcompartments with their valves are placed at opposite ends of the pumpcylinders, and require two boxes which are under the high oil columnpressure. In the construction illustrated in FIG. 5b the two pumpingcompartments with their valves are placed between the two cylinders ofthe pump, being separated by a common wall through which passes thedriv- 6 ing rod for both pistons and which needs only one stuffing-boxworking under high pressure.

As control means for interrupting and reestablishing the current in theelectric motor winding, when the running direction thereof is changed, astatic switching device is used, which in case of the constructionillustrated in the electric circuit diagram of FIG. 6 uses saturantreactors.

In this diagram K represents the automatic switch of the device; u, vand w represent the three phases of the secondary winding of thetransformer T feeding the electric pump from ground level the primarywinding of which is connected by a three conductor cable, the windingsSu, Sv and Sw of the electric motor stator. The saturant reactors Rv andRw are mounted in the phases v and w.

Inside the housing of the electric pump there are mounted two coils 26and 26 provided with the magnetic cores 27 and 27 fed in series througha singlephase circuit connected in parallel on the voltage of the phaseu, and closing through the mass of the discharge duct and the primarywinding of a transformer-rectifier group TR the secondary circuit ofwhich is feeding the existing coils of the saturant reactors Rv and Rwwith rectified current.

When the pump is working by electric drive the magnetic cores 27 and 27'are being taken out of the coils 26 and 26', their reactance isnegligible and the group transformer rectifier TR is feeding the excitedcoils of the reactors Rv and Rw saturating them, so that their reactanceis negligible and the electric motor is fed from the network.

The magnetic cores 27 and 27' shift with the movement of the mobilearmature A of the electric motor, so that when the armature arrives at acertain established distance from the up-stroke, respectively thedown-stroke end, the corresponding magnetic core is introduced into thecoil 26 (respectively 26'), producing an increase in the reactance ofthe coil, which reduces to about Zero the current in the feeding circuitof the group transformer-rectifier TR, causing the suppression of theexciting of the saturant reactors Rv and Rw and thereby introducing inthe circuit of these two phases reactances which practically cancel thethree-phase feeding current of the electric motor.

After reversing the moving direction of the mobile armature when itarrives at the predetermined distance from the stroke end, the magnetcore is pushed out of the respective coil 26, 26 and the current isreestablished in the exciting circuit of the saturant reactors R11 andRw, as well as in the three-phase electric motor feeding circuit.

The reversal of the electric motor magnetic field shifting direction atstroke ends is realized by reversing the phases 1/ and w by means of aswitch 28, actuated by the movement of the mobile armature A shifting inthe interval in which the current is interrupted in the circuit, theswitching of the phases being realized without any current. In order toavoid working with a single phase resulting in an overload, in whichcase the voltage would be interrupted in one of the phases v or w, theautomatic break switch K is provided with zero voltage relays in eachone of its three phases.

The same control means can also be used when instead of using thesaturant reactors Rv and Rw, electronic devices (i.e. transistors) areused which would be placed either at the surface or inside the electricmotor housing.

In the case of a voltage breakdown (deliberate or accidental) in orderto avoid, when the power is restored, the danger of a starting underfull load by electric drive from any position, which would require theuse of an oversized electric motor, the discharge line of the electricpump is provided with a three-way valve 29 FIGS. 5a and 5b, controlledby an electromagnetic relay 3%) having zero voltage, mounted on thephase 1!.

sure acting from outside, the weight of the mobile arma-.

ture in any position, would determine its downward displacement to thedown-stroke end, where a cam with rectilinear motion 33, mounted on thepiston rod 22, is causing the lever 32 to come back to the workingposition x, further causes the relay 30 to reset itself and the cam 33to lock in position thereby bringing the pumps -P and P to the end oftheir down stroke.

When the voltage is reestablished, the relay 30 unlocks the cam 33 andthe electric pump is placed again in starting position by the hydraulicdrive, as it is at each motion direction reversal.

Instead of the above described three-way valve 29, two oppositelyworking valves (push-pull) can be used, one. of these valves would bebuilt in the discharge pipe in the tubing and the other in the outsidedischarge duct, the valves being controlled by a common voltage relay orby two different relays, so that when the voltage fails, the dischargevalve toward the tubing will be closed and the discharge valve towardthe outside will be open, and when the voltage is reestablished thedischarge valve toward the outside is closed and the discharge valvetoward the tubing is opened.

The pumping device of this invention can be constructed with only onepump. In this case, at the upstroke, the motor is used for lifting themobile armature and at the down-stroke the pump is driven as well by theforce produced by the motor and also by the weight of the mobilearmature.

When the hydraulic drive is used for starting, at the changing ofdirection, the movement of the mobile armature, while the electric driveis being used only in the device in a constant speed operation, theelectric motor can be built as a synchronous motor, replacing therebythe mobile armature with a cage with a mobile armature of similarconstruction, but provided with excitation coils mounted in slots andfed with direct current, obtained from a transformer-rectifier groupconnected in parallel with the electric motor feeding circuit, or from agenerator, driven by the mobile armature motion.

The utilization of the synchronous motor for driving the pump has thefollowing advantages when compared with the asynchronous motor:

The power factor can have a value close to one, the losses in statorwindings for the same useful power are reduced to less than a half,because due to the great number of pole pairs, the value of the powerfactor in such an embodiment is under 0.7.

For the same losses and respectively of the current in the stator, theelectric motor power is increased with 40-50% by comparison to anembodiment using an asynchronous motor.

For the same electric motor dimensions, the air gap of the synchronousmotor can be considerably increased, a fact which facilitates themanufacture of stators of great length and respectively of more powerfulmotors.

The driving of the pumping device of this invention can also beperformed with a single-phase motor which has the following advantages:

It allows the use of a single conductor cable, the current return beingachieved through the discharge duct.

It is possible to eliminate the switch used for reversal of the phases.

On the other hand, the use of a single-phase motor 8 presents in turnthe disadvantage of a slight increase in losses.

For feeding the electric pump with electric power, especially when it isworking at a great depth, and in order to realize the most favorableconditions from the windings insulation point of view, there can be usedtwo single-phase transformers which are mounted in stages over theelectric pump to reduce the supply voltage.

Based on a dimensioning calculation, in case an induction three-phasemotor is used, it has been noted that an electric motor having a pumpingfrequency of 30 double strokes per minute (the length of stroke 3.50m.), which can pump 80 tons of oil in 24 hours from a depth of 1500 m.and which can be introduced in a casing having an interior diameter of120 mm., will have an efficiency of 0.7 and a stator height of about2.6-0 m.

Taking into account also the two extensions (of smaller diameter) of thehousing for the stroke of the mobile armature, the total electric motorlength is not greater than 10 In.

The advantages of the electric motor according to this invention, arebecoming more evident as the pumping depth increases, because the pumpconstruction and the operation are not at all influenced by theincreasing depth, if the driving force and respectively the power aremaintained constant; consequently, the same electric motor used for acertain depth can be also used at a much greater depth if a pump is usedwhich has an output inversely proportional to the depth.

What is claimed is:

1. A pumping system adapted to be mounted in the casing of Wells,comprising in combination, an electric induction motor, having anaxially reciprocally moving armature operatively mounted in said motor;a doublepumping means reciprocally mounted in said casing, and

coaxially connected to said armature of said electric m0- tor; saiddoublepumping means include means for discharging liquid via said casingand also include means for exerting on said armature pressure producedby the column of discharging liquid immediately after reversal of motionof said armature, in the direction of movement thereof; and an electric.power source operatively. connected to said electric motor.

2. The pumping system as set forth in claim 1, wherein saiddouble-pumping means comprise a pump housing and two pistons coaxiallyreciprocally mounted therein, said two pistons being respectivelyconnected to each other and to said armature of said electric motor bymeans of an axially extending piston rod, whereby immediately afterreversal of motion, one of said two pistons is idling whereas the otherone is under pressure by said column of discharging liquid.

3. The pumping system as set forth in claim 1, including electricswitching means operatively connecting said electric motor to saidelectric power source, for electrically energizing alternately inopposite polarities the stator of said electric motor, saidelectricswitching means including saturant reactor means, an actuating memberoperatively connected to said saturant reactor means and mechanicallylinked to said armature, thereby disconnecting said electric powersource from said armature at a preselectedpoint near the end of itsstroke and reconnecting said electric power source at said preselectedpoint near the beginning of the next opposite stroke, said armaturebeing actuated hydraulically by said double-pump means in theintervening period.

4. A-pumping system as set forth in claim 2, wherein said pump housing(1) of said electric motor is cylindrical, said motor includes aplurality of stators (e.g. six stators 8 -8 which are made out of sheetpacks and which are disposed on a circle in said housing (1) and haveslots (3) in which a plurality of annular coils (4) are mounted, eachcoil passing from the slot of one stator directly into the slot of theadjacent stator, said plurality of coils being connected in series sothat each coil is mounted in a pair of oppositely positioned stators ofsaid plurality of stators, so that when said plurality of coils areconnected to said electric power source so as to form windings which arefed with three-phase currents a magnetic field will be produced in saidplurality of stators with an alternating rectilineal motion which willactuate upon said armature A, the latter being provided with a cageconstituted out of annular conductors which are mounted in slots of saidarmature A.

5. A pumping system as set forth in claim 4, wherein in said housing ofsaid motor there is provided a cooling fiuid (insulating oil or air)which, due to the displacement of said armature, circulates through freespaces (ll ll between said housing and terminals of said plurality ofcoils which exit from one stator and extend into the adjacent stator ofsaid plurality of stators; a plurality of small bafiie plates extendingradially inwardly from the interior wall surfaces of said housing, saidplurality of small baftle plates serving to conduct the cooling liquidin such a manner as to wash all the better the surfaces of said statorwindings.

6. A pumping system as set forth in claim 5, wherein said electric motor(M) is connected to said two pistons (22, 22', 22a, 22'a) by means ofsaid piston rod (7, 21), a pair of valves (18, 18) operatively mountedin the walls of said pump housing, a pair of cams (23, 23') respectivelyprojecting from said two pistons (22, 22', 22a, 22a) and being given areciprocal rectilinear motion by said armature (A), said pair of cams(23, 23') being adapted to cooperate with said pair of valves (18, 18'),said pump housing including a pair of openings (20, 20) in the wallsthereof which are positioned so as to cooperate with said two pistons(22, 22', 22a, 22a); whereby said pair of cams (23, 23') are adapted tomaintain open the corresponding valve of said pair of valves (18, 18')at the end of the discharge stroke of a corresponding piston of saidpair of pistons until said piston has started its motion in the reversedirection and has accelerated to normal speed at which time the actionof said armature via said piston rod (7, 21) takes over; while saidvalve remains open as set forth above, a hydraulic pressure is exertedon said piston by a column of liquid being discharged Which is incommunication with said piston via said valve while the other piston ofsaid two pistons (22, 22, 22a, 22a) is in communication with theinterior of the well casing via an associated opening of said pair ofopenings (20, 20').

7. A pumping system as set forth in claim 6, including a safety devicearrangement which comprises, a third coil (30) electrically connected tosaid third conductor (U), a second magnetic core reciprocally movablymounted in said third coil, three-way valve means (29) operativelymounted in said pump housing so as to control the outlet thereof, saidthree-way valve means (29) being operatively connected to said secondmagnetic core in such a way that when the voltage is cut off in saidthird conductor (U) said electric motor (M) and said third coil (30) arede-energized, whereby said three-way valve means (29) move from anoutlet-open position to an outlet-closed position and place said housingin direct communication with the interior of said casing, said twopistons (22, 22, 22a, 22'a) sinking to the bottom of said pump housing(17) due to their own gravity, and means (32, 33) operatively connectedto said three-way valve means (29) for returning the latter tooutlet-open position when said two pistons (22, 22', 22a, 22a) havereached their respective bottom positions.

8. A pumping system as set forth in claim 6, including means forinterrupting and reversing the current from said source of electricpower, the latter being of the threephase alternating current type andincluding three conductors (U, V. W) which are operatively connected to10 said electric motor, two saturant reactors (Rv, Rw) respectivelyoperatively connected to two conductors (V, W) of said three conductors,the third conductor (U) of said three conductors being connected to acontrol circuit means, the latter being electrically connected to themass of said pump housing and said third conductor (U) and including twoseries-connected coils (26, 26), two magnetic cores (27, 27')reciprocally movably mounted in said two coils (26, 26') respectivelyand being mechanically connected to said armature (A) and electricallyconnected to said two saturant reactors (Rv, Rw) respectively, wherebydepending on the positions of said two magnetic cores (27, 27) in saidtwo coils (26, 26') respectively said two saturant reactors (Rv, Rw)render said two conductors (V, W) electrically conductive ornon-conductive thereby controlling the energizing of said motor by saidelectric power source.

9. A pumping system as set forth in claim 7, wherein hydraulic drivingpower is used for starting the stroke of said armature (A) and forelectrically driving at constant speed a single-phase asynchronous motor(M) is used.

10. A pumping system as set forth in claim 7, wherein a single pump (P)is used; in the up-stroke the electric motor (M) is used to raise theweight of the mobile armature (A), and in its down-stroke the driving ofthe pump (P) is effected, partly by the weight of the armature (A) andpartly by the drive of the electric motor (M).

11. A pumping system as set forth in claim 7, wherein the interruptingand the reversal of the current for the electric motor havingalternating rectilinear motion is obtained by means of electronicdevices, controlled by the motion of the mobile armature in similarconditions as the controlling saturant reactors Rv and Rw.

12. A pumping system, as set forth in claim 1, characterized by the factthat, for breaking the current, when the moving direction is reversed,static means for switching are used, e.g. saturant reactors, controlledby the motion of the mobile armature, so that between the moment of thebreak-off of the current and the moment of its re-establishing in thereversed stroke a displacement must exist during which the decelerationand the acceleration in opposite direction of the mobile garniture isachieved by hydraulic drive, so that the current will be re-establishedonly after the normal speed has been reached.

13. A pumping system as set forth in claim 12, using an electric motor(M), which drives directly with rod 7 the pistons of two pumps (P andP), characterized by the fact, that the pumps have discharge valves (18and 18'), controlled by cams with rectilinear motion (23 and 23')actuated by the motion of the mobile armature, so that these valvesremain open after the discharge stroke is finished, when the electriccurrent is interrupted at the end of the stroke, making it possible thatthe starting in opposite direction and the acceleration up to normalspeed, when electric drive begins, will be realized by the hydraulicdrive, due to the pressure exerted by the column of discharged oil onthe respective piston (P and P) and by establishing a directcommunication for the pressure between the bore hole and the otherpiston (P' and P) through the windows (20' and 20).

14. A pumping system as set forth in claim 13, characterized by the factthat the interruption and the reversal of the current in the drivingelectric motor with alternating rectilinear motion are realized with thehelp of saturant reactors (Rv and Rw) placed on the feeding conductors(v and w) excepting conductor (U), which feeds the control circuit, acircuit connected between the respective phase and the mass and in whichtwo reactance coils (26 and 26') are intercalated, into which twomagnetic cores (27 and 27) are introduced at each stroke end by themotion of the mobile armature, determining the suppression of thecontrol current and thereby the interruption of the feeding current.

15. A pumping system as set forth in claim 14, characterized by thefact, that to the using of the hydraulic drive for starting, the workingby electric drive is performed with constant speed, using a synchronousmotor with alternating rectilinear motion the exciting winding of whichis fed with a rectified current from a transformer-rectifier unit,connected to the main feeding circuit, or from a generator, actuated bythe motion of the mobile armature.

References Cited UNITED STATES PATENTS Newcomb 10346 Schmidt 10353Coberly 103-46 X Winsor 103-46 X Hobitzelle 103-46 ROBERT M. WALKER,Primary Examiner.

1. A PUMPING SYSTEM ADAPTED TO BE MOUNTED IN THE CASING OF WELLS,COMPRISING IN COMBINATION, AND ELECTRIC INDUCTION MOTOR, HAVING ANAXIALLY RECIPROCALLY MOVING ARMATURE OPERATIVELY MOUNTING IN SAID MOTOR;A DOUBLEPUMPING MEANS RECIPROCALLY MOUNTING IN SAID CASING, ANDCOAXIALLY CONNECTED TO SAID ARMATURE OF SAID ELECTRIC MOTOR; SAIDDOUBLE-PUMPING MEANS INCLUDE MEANS FOR DISCHARGING LIQUID VIA SAIDCASING AND ALSO INCLUDE MEANS FOR EXERTING ON SAID ARMATURE PRESSUREPRODUCED BY THE COLUMN OF DISCHARGING LIQUID IMMEDIATELY AFTER REVERSALOF MOTION OF SAID ARMATURE, IN THE DIRECTION OF MOVEMENT THEREOF; AND ANELECTRIC POWER SOURCE OPERATIVELY CONNECTED TO SAID ELECTRIC MOTOR.